1. Field of the Invention
The present invention relates to an apparatus for preventing accidental recording of a cassette type tape recorder, and particularly to an apparatus for preventing accidental erasure or double recording on a cassette tape of a tape recorder utilizing a reel rotation sensing mechanism which senses rotation of a reel disk.
2. Description of the Background Art
Magnetic recording medium is generally capable of recording and reproducing desired information repeatedly as wanted.
The magnetic recording medium is cut to a predetermined width, wound onto reels, and a tape cassette is made up by installing the reels in a casing. The tape cassette and a tape recorder for driving the tape cassette are provided with a mechanism for preventing accidental recording, i.e., erasure or change of the recorded contents against the user's intention. In more detail, the tape cassette is provided with a removable protecting piece for preventing accidental recording and the tape recorder is provided with a detecting mechanism for checking the presence of the protecting piece to automatically determine the allowance or prohibition of recording.
For example, in the Japanese U.M. Laid Open No. Sho 60-26833, there is disclosed a technique wherein an operating key of the recording mode is pushed down or not pushed down by a detecting member for detecting the presence of the protecting piece of the cassette. However, this technique is not suitable for an apparatus such as a VTR, which is also known as a VCR, in which almost all of the operating keys are of a switch operation type.
Japanese U.M. Laid Open No. Sho 58-193342 and the U.S. Pat. No. 4,506,122 respectively disclose a recording preventing apparatus and a switch thereof wherein a selection switch is activated by a detection lever for detecting the presence of the protecting piece of the tape cassette, and a device for prohibiting the recording mode upon receiving a switching signal from the selection switch. In these techniques, the contacts of the selection switch must be preserved in good condition for assuring operation. But, the contacts of the switch are apt to be deteriorated to cause mis-operating due to sparks initiated by frequent contact and separation, or due to the weakening of contacting force between contacts.